Impaired movement of the upper extremities often accompanies neuromuscular disorders such as stroke, spinal cord injury, multiple sclerosis, peripheral nerve damage and arthritis. The motor deficits result in a loss of independence, reduced quality of life and high costs of care. Stroke is the leading cause of upper extremity dysfunction. In developed countries, about 1.5% of the population live with the after-effects of stroke or about 5.5 million people in North America (American Heart Association, 2006). Functional recovery of the upper extremity after stroke is quite poor, with 55% to 75% of patients having significant permanent deficits in performing activities of daily life (Lai et al., 2002).
The most widely used rehabilitative techniques are Neuro-Developmental Treatment and Proprioceptive Neuromuscular Facilitation. Both are forms of exercise therapy which have been shown to be effective if performed on a regular basis over weeks or months (Dickstein et al., 1986). Another technique, Constraint Induced Therapy, was recently developed specifically for the rehabilitation of upper extremity function and involves intensive exercise therapy of the affected arm and hand, typically six hours per day for two weeks (Taub et al., 1999). Constraint Induced Therapy has been widely adopted around the world since large gains in function of the hemiplegic extremity in activities of daily life are achieved after two weeks.
However, the above techniques are time-consuming for therapists in that such techniques require one-on-one supervision, ideally on a daily basis. Furthermore, the types of exercises involved tend to vary from one treatment facility to another. Reimbursement is usually limited to the time patients are in a rehabilitation hospital. Following a hospital stay, patients are required not only to travel to physical therapy clinics, but also to absorb the costs of such services themselves. Such disadvantages prevent the large majority of potential beneficiaries of exercise therapy from receiving it.
Those skilled in the art have attempted to provide methods and devices suitable for machine delivery of exercise. For example, U.S. Pat. No. 6,007,459 to Burgess describes the use of an interactive video communications link which allows a therapist to supervise exercises performed by subjects located elsewhere, for example in their homes.
Another approach is to provide a subject with an interactive robotic system attached to the subject's limb. For example, U.S. Pat. No. 5,466,213 to Hogan et al. describes a robot which guides the limb along desired movement paths comprising a series of upper extremity exercises. The subject's robot can also be controlled remotely by a physical therapist using a second identical robot. The system can include a teleconferencing system allowing subject and therapist to communicate with each other. However, this technology is highly expensive, precluding it from widespread usage.
Other devices that impose movements on the hand have been suggested. For example, U.S. Pat. No. 5,746,704 to Schenck et al. teaches a motorized exercise device for imposing movements along a specified path on a digit of the hand. Such passive motion devices are problematic, either in being limited to particular anatomical parts such as a single digit, or not enabling active exercise of a representative range of upper extremity movements required for activities of daily life.
U.S. Pat. No. 5,755,645 to Miller et al. teaches a multiple degree of freedom passive exercise device in the form of a joystick with a telescopic arm, whereby the user grasps a handle and moves it in a three-dimensional workspace. Computerized control of two or more brakes creates programmable mechanical resistances within the workspace. This device allows the performance of many types of movement such as throwing a ball or swinging a baseball bat. Handle attachments including tennis rackets, golf clubs and hockey sticks are described. However, the complexities of the mechanism, controllers and software place this device into a price category unaffordable for widespread distribution into peoples' homes. U.S. Pat. No. 6,988,977 to Webber et al. describes a passive exercise device with a multi-jointed arm. This device is intended as part of a weight-lifting machine for upper body training. Both Miller et al. and Webber et al. describe manipulanda in the form of handles which are easily grasped; yet, such manipulanda are not even representative of the differently sized and shaped objects encountered in activities of daily life and which are most problematic for people with impaired hand function.
Exercise workstations have been designed with instrumented objects of different sizes and shapes and sensors attached to the objects to provide kinematic data to a computer. Gritsenko et al. (2001) describes a workstation in the form of a desk surface, with fixed objects such as a spring-loaded doorknob, a spring-loaded caliper, a weighted handle and loose objects such as blocks and cylinders. Gritsenko and Prochazka (2004) describes a workstation in the form of a circular table with a rotatable upper surface, bearing a similar range of fixed and loose objects. Taub et al. (2005) describes a cabinet with eight sets of fixed and loose objects arrayed on four work surfaces, each of which may be selected and manually pulled toward the subject from the cabinet. All of the described workstations are difficult to adjust, mechanically complex, bulky and expensive, rendering them undesirable for widespread usage in peoples' homes.
U.S. Pat. No. 6,613,000 to Reinkensmeyer et al. describes a more affordable passive exercise device. A mass-produced computer input device such as a joystick intended for computer games is used by the subject to perform hand movements. Signals from the joystick sensors are used to provide input to a computer that communicates to a server computer through a computer network. The server computer downloads individualized information to the subject's computer, specifying desired therapy and assessment exercises. The therapy and assessment exercises can be performed autonomously without real-time supervision from a therapist. The drawback of the device is that the range of movements performed by the subject is limited to the motion of the top of the joystick, namely a curved surface. The joystick knob is relatively easy to grasp, unlike many objects encountered in activities of daily life.
There is clearly a need for an inexpensive, straightforward device which addresses significant daily tasks such as grasping, lifting, lowering, moving side-to-side, twisting and otherwise manipulating objects of different sizes and shapes.